Valence bond theory

d block element and transition elements forms complex ion

 

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Complex ion formation by d block element and transition element

d block and transition elements forms complex ion. This can be explain by valence bond theory. Ligand that have lone pair electron strongly effect on central atoms d orbital if d orbitals unpaired electron can be maximum paired with opposite spin. For that reason there will create unoccupied blank orbital. These blank orbital will mixed with each other and form hybrid orbital. These hybrid orbital will be capable to receive electron donated from lone pair electron of ligand. Therefore, there will be create a coordinate bond between ligand and central atom. With this mechanism d block elements and transition elements forms complex ion.

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Crystal field theory and coloured compound

Crystal field theory

Crystal field theory explains how transition element, d block element, and complex ion forms coloured compound.

Complex ion have two parts. One is central ion and rests are Ligand connected to central ion by coordinate bond. Ligand have lone pair electron. Lone pair electron of ligand have strong effect on d orbitals of central ion. Lone pair electron of ligand will very strongly repulse on dx²-y² and dz² than others. For that reason 5 d orbital will separated into high energy state and low energy state.  

dxy, dyz, dzx are in lowest energy state and dx²-y², dz² will be in highest energy state. There have a energy difference between them equal to ∆E, which is the main mysterious of creating color.

If the value of ∆E match with any wavelength of visible light then lowest energy state orbitals electron will absorb energy from visible light equal to ∆E and will jump to highest energy state. Again, it will return back to lowest energy state by jumping by emission of energy. This emission of wavelength energy visible as colour based on animals capabilities.

Coloured compound and Crystal field theory

d block element and transition element forms complex ion

Mechanism of complex ion formation

Techniques of some chemical measurement

Lanthanides forms ionic compound but actinides forms covalent compound

 The elements lanthanum to Lutessium is lanthanides. Actinium to lawrencium is actinides. Both element shows contraction. That means sudden reduction of atomic radius. The cause of contraction is shielding effect of 4f orbital in lanthanides and 5f orbital in actinides.

Shielding effect by 5f orbital is very poor than shielding effect by 4f orbital. Because, 5f orbital is more diffuse and extended and out spread. Hence, actinides can form covalent compound.

Innert gas have greater ionization energy

 Though, innert gas is inactive and can not do reaction and it have highest stable electronic configuration. Removing any electron from its outermost electronic shell is very difficult and probably impossible. Hence, it's ionization energy is greater.

Lanthanides have lower ionization energy

 In lanthanides series from lanthanum to lutessium, atomic radius of elements sudden drops due to complex structure of 4f orbital. Due to its complex structure 4f orbital contains large number of lobes and these are out spreads. As a result 4f orbital can not causes strong shielding effect between nucleus and outermost electron. Hence, Nucleus attract outermost electron strongly. Hence, Sudden drop of atomic radius causes. This dropping of atomic radius in lanthanides are called lanthanides contraction. As a result it's ionization energy increases from Cs and Barellium. The elements of lanthanides IE shows slowly increase. All of the elements of lanthanides IE approximately simar and nearest due to f orbitals poor shielding. 

Cs have lowest Ionization energy

 Among the stable element Cs have lowest ionization energy because of it highest atomic radius that have been possible for stronger shielding effect inside itself. 

Though, Fr ionization energy is more less than Cs in really, but it can not measure properly because of its radioactivity.

 Ionization energy 

Ionization energy is required energy to remove an electron from outermost shell of an isolated atom. 

The electron that is more distance from nucleus feels less attraction by nucleus. Hence, to breakdown this less attraction atom required less energy. Hence, Ionization energy will be less.

That means, electron more distance from nucleus have less ionization energy. Atomic radius increases Ionization energy increases. In a periodic table left to right in a period Ionization energy increases. Because, atomic radius decreases from left to right in a periodic table due to gradually increasing of electron number in same energy state. But yet some difference are found,

For example, B placed in right side than Be in a periodic table in 2nd period. B have less ionization energy than Be

As same, Oxygen's ionization energy is less than Nitrogen

Energy required to remove first loosely bounded electron from outermost electronic shell is First Ionization energy. After that required energy to remove 2nd electron is 2nd Ionization energy. And energy required to remove 3rd electron is called 3rd ionization energy. 

2nd and 3rd ionization energy is very large from first Ionization energy., Because when any atom remove a one electron, it convert into positive charge. Highest positive charge attract more stronger to outermost electron in cation than neutral atom. Moreover, ions electronic configuration more closer to noble gas and more stable structure. Hence, 2nd Ionization energy will be larger than 1st ionization energy. 3rd Ionization energy be more larger than 2nd Ionization energy. 

The more the stable electronic configuration, ionization energy will be more higher. For example, Innert gas have highest ionization energy

Exactly, Ionization energy mainly depends of atomic radius. Certain factors influence impacts on atomic radius. For example, shielding effect and different orbital existence. 

Among all other stable elements Cs have lowest ionization energydue to shielding effect. 

Lanthanides ionization energy dramatically increases because of declining atomic radius. This declining of radius is called lanthanides contraction.

Oxygen ionization energy is less than Nitrogen

 

In periodic table the position of oxygen to right from Nitrogen. But yet, Oxygen's ionization energy is less than Nitrogen. Because, Instead of declining Oxygens atomic radius increases. Electrostatic attraction between Nucleus and outermost electron reduces. Why happens this? In the electronic configuration of Nitrogen every P orbital is filled by single electron, But In terms of Oxygen one of the P orbital filled by double electron with opposite spin. This causes electron electron repulsion between two electrons in a small orbital. One electron tends to displaced other electron. Moreover, If the two electron are very nearest, One electron that is nearest to nucleus creates a sheilding effect between the attraction of outermost electron and nucleus. As a result, Attraction to Nucleus reduces. Hence, outermost electron get more chance to be distance from nucleus. Energy requirement to remove outermost electron decreases. Hence, Ionization energy decreases.

B have less ionization energy than Be

 B shows less Ionization energy than Be 

Rutherford alpha particles scattering experiment

Rutherford alpha particles scattering experiment

Hybridization

Hybridization

 Hybridization is a process of form new orbital by mixing with more than one different orbital as possible as it can form bond. New formed orbital consisting different orbital is called hybrid orbital.

For example, 

One S orbital and One P orbital mixes and forms SP hybrid orbital.

One S orbital and two P orbital mixes and form SP² hybrid orbital.

One S orbital and three P orbital mixes and forms SP³ hybrid orbital.

SP hybrid orbital is linear, the molecule formed by central atom with SP hybridized will be linear in structure. Bond angle will be 180 degree. 

The molecule where central atom is sp² hybridized will be trigonal planner. Bond angle will be 120 degree.  In ethene there have two central atom. Each atom bonded with one carbon and two hydrogen. Each of the sigma bond will be in same trigonal  plane. 

SP³ hybrid orbital is tetrahedral in structure. Hence, molecule will be tetrahedral. Bond angle will be 109,5 degree. Methane is tetrahedral in structure.

Though

Quantum number

Quantum number is a set of number to express position, orientation and spin of electron within an atom. 

 It express the Size and shape of elliptical path, three dimensional orientation of orbitals and electrons spin. 

 There have four quantum number 

Principle quantum Number

Azimuthal quantum Number

Magnetic Quantum Number

Spin quantum Number

 Principle quantum number

 The number to express size of energy state. it expresses in which energy state electron placed. If electron placed in 3rd energy state, principle quantum number is 3. it is expressed as n. Azimuthal quantum number depends directly on the value of n. Magnetic quantum number depends directly on azimuthal quantum number and indirectly on principle quantum number.

 Azimuthal Quantum number

Azimuthal Quantum Number expresses the sub shell in the energy state. It expresses how number subshell exist within an energy state. It is expresses as l. its value depends on the value of n. its value will be 0 to n-1. 

In 3rd energy state n equal to 3. Hence, azimuthal quantum number will be 0, 1, 2. Hence, s, p, d, orbital is possible in 3rd energy state. 

 Magnetic Quantum Number

  Magnetic Quantum Number expresses orbital number and orientation of orbital. How number of orbital is possible and what types of orbital is possible within an energy state magnetic quantum number indicates it. It's value depends on azimuthal quantum number. For any value of l, it is equal to 2l+1. In 3rd energy state l have value 0, 1, 2. Hence, Magnetic quantum number will be is as bellow, 

For l is 0, magnetic quantum number is 1. Hence a one S orbital is possible in 3rd energy state. 

 For l is 1, magnetic quantum number will be -1, 0, +1 Hence, three orientation of p orbital exist. Px, Py, Pz 

For l equal to 2, Magnetic quantum number will be -2, -1, 0, +1, +2 Hence, 5 orientation of d orbital is possible in 3rd energy state. 

 In 3rd energy state total number of orbital is equal to 9. Spin quantum Number: The spin of electron will be + half and - Half.

Polarization

 Polarization

polarization is a process of forming dipole die to electronegativity difference between two atom bonded. Due to electronegativity difference, more electronegative atom or ion attract electron cloud of other atom or ion to itself. For that reason it turned into partially negative and another atom from where electron is attracted become partially positive. The compound develops two pole with oppositely charged. This compound is called dipole. The following factors are effective for polarization. Cation size Electronegativity difference